I encountered another problem that returns the same error.

Single quote issue

I used a json string with single quotes :

{
    'property': 1
}

But json.loads accepts only double quotes for json properties :

{
    "property": 1
}

Final comma issue

json.loads doesn’t accept a final comma:

{
  "property": "text", 
  "property2": "text2",
}

Solution: ast to solve single quote and final comma issues

You can use ast (part of standard library for both Python 2 and 3) for this processing. Here is an example :

import ast
# ast.literal_eval() return a dict object, we must use json.dumps to get JSON string
import json

# Single quote to double with ast.literal_eval()
json_data = "{'property': 'text'}"
json_data = ast.literal_eval(json_data)
print(json.dumps(json_data))
# Displays : {"property": "text"}

# ast.literal_eval() with double quotes
json_data="{"property": "text"}"
json_data = ast.literal_eval(json_data)
print(json.dumps(json_data))
# Displays : {"property": "text"}

# ast.literal_eval() with final coma
json_data = "{'property': 'text', 'property2': 'text2',}"
json_data = ast.literal_eval(json_data)
print(json.dumps(json_data))
# Displays : {"property2": "text2", "property": "text"}

Using ast will prevent you from single quote and final comma issues by interpet the JSON like Python dictionnary (so you must follow the Python dictionnary syntax). It’s a pretty good and safely alternative of eval() function for literal structures.

Python documentation warned us of using large/complex string :

Warning It is possible to crash the Python interpreter with a
sufficiently large/complex string due to stack depth limitations in
Python’s AST compiler.

json.dumps with single quotes

To use json.dumps with single quotes easily you can use this code:

import ast
import json

data = json.dumps(ast.literal_eval(json_data_single_quote))

ast documentation

ast Python 3 doc

ast Python 2 doc

Tool

If you frequently edit JSON, you may use CodeBeautify. It helps you to fix syntax error and minify/beautify JSON.